1. Field of the Invention
This invention relates generally to high pressure pasteurization and more specifically to a method and apparatus for use while utilizing high pressure pasteurization for food products.
2. Description of the Prior Art
Consumers desire high quality, minimally processed foods with fresh characteristics and little to no additives. High pressure pasteurization (“HPP”), also known as high hydrostatic pressure processing or ultra-high pressure processing, is being used to pasteurize foods at elevated pressures of approximately 30,000 to 130,000 pounds per square inch (“psi”) for a specified temperature and time. The pressure is applied through a pressure medium such as a liquid or a gas. Under these conditions, HPP has been found to be effective in inactivating many pathogenic microorganisms commonly found in foods. As compared to canned foods or pasteurized juices and milk, HPP significantly reduces the process temperature and time, which results in foods with improved characteristics such as better retention of freshness, flavor, texture, color, and nutrients.
HPP is based on the Le Chatelier principle which states that a system at equilibrium adjusts when subjected to a stress and that actions that have a net volume increase will be retarded and actions that have a net volume decrease will be enhanced. HPP utilizes isostatic or hydrostatic pressure which is equal from every direction. Isostatic compression transfers pressure instantly and uniformly throughout the pressure medium providing a non-thermal process alternative for the pasteurization of temperature-sensitive foods. Foods suspended in the pressure medium are assumed to follow the isostatic principle. The basis for using the HPP process as a pasteurization method is based on the assumption that the product also follows the isostatic rule, which states that isostatic pressure is instantly and uniformly transmitted throughout the pressurized medium and the enclosed food product, regardless of size, shape or physical state of the food.
During HPP, foods are subjected to pressures up to 130,000 psi, and the pressure destroys pathogenic microorganisms by interrupting their cellular functions. Within a living bacteria cell, many pressure sensitive processes such as protein function, enzyme action, and cellular membrane function are impacted by high pressure resulting in the inability of the bacteria to survive. Small macromolecules that are responsible for flavor, order, and nutrition are typically not changed by pressure.
HPP is gaining in popularity within the food industry because of its capacity to inactivate pathogenic microorganisms with little to no heat treatment, resulting in the retention of most of the nutritional and sensory characteristics of fresh foods without sacrificing shelf-life of the foods.
One of the advantages of HPP is that pressure transmission is relatively instantaneous and uniform, and HPP is not controlled by product size and is effective throughout the foods. HPP also offers several advantages over traditional thermal processing including reduced process times, minimal heat damage, and retention of freshness, flavor, texture, color, and nutrients.
To date, the process for HPP has been on a much smaller scale than is typically needed for processing large quantities of food. The present invention addresses this problem and provides for a new method and an apparatus for use during the high pressure pasteurization.